FIG. 1 illustrates a phased array antenna system 10 using a space feed technique to distribute energy to a mulitiplicity of active electronic modules. Each electronic module 11 receives energy from a primary feed 12. The energy is amplified, shifted in phase, and radiated into space. Phase shifters 13, when properly set, cause the phase front to reinforce in a particular direction which, in turn establishes a beam-pointing direction.
One problem with phased array antennas is the reduction of array performance due to the effects of mutual electromagnetic coupling between radiating elements of the array. This coupling, which is frequency dependent and a strong function of scan angle of the phased array, causes an imperfect impedance match at the feed points of each radiating element in the array. This results in increased side lobe levels, degradation of the beam shape produced by a phased array antenna, deterioration of polarization characteristics, and increased heating due to a reduction of antenna efficiency. Under severe conditions, such mutual coupling can also lead to scan blindness in phased array antennas. Scan blindness occurs when a phased array beam is steered to a specific angle, and the elements of the array have a large impedance mismatch with their feed circuits. This results in little or no power being transmitted, such that the array is "blind" at that specific angle.
A device is needed for reducing or eliminating these effects to maximize the performance of a phased array antenna.